2022/03/03 by Ning-Chen Sun, Justyn R. Maund, Paul A. Crowther +2
Physics and Astronomy · #Astro and Planetary Science #Astronomy #Astrophysics #Gamma-ray bursts and supernovae #Laser-Plasma Interactions and Diagnostics #Physics #Transient (computer programming) #astro-ph.HE #astro-ph.SR
paper · pdf · doi:10.1093/mnrasl/slac023
5 pages, 4 figures, accepted for publication in MNRAS Letters
arxiv created 2022/03/03 · openalex publication_date 2022/03/04 · openalex created_date 2022/03/05 · arxiv updated 2022/03/14 · openalex updated_date 2026/08/05
We report the discovery of a luminous late-time source at the position of the fast blue optical transient (FBOT) AT2018cow on images taken by the Hubble Space Telescope (HST) at 714 d and 1136 d after its explosion. This source is detected at both UV and optical wavelengths and has prominent Hα emission. It has a very stable brightness between the two epochs and a very blue spectral energy distribution (SED) consistent with fλ ∝ λ-4.1 ± 0.1, i.e. the Rayleigh-Jeans tail of a hot blackbody with a very high temperature of log(T/K) > 4.6 and luminosity of log(L/L_\odot) > 7.0. This late-time source is unlikely to be an unrelated object in chance alignment, or due to a light echo of AT2018cow. Other possible scenarios also have some difficulties in explaining this late-time source, including companion star(s), star cluster, the survived progenitor star, interaction with circumstellar medium (CSM), magnetar, or delayed accretion in a tidal disruption event (TDE). Long-term and multi-wavelength monitoring will help to resolve its nature and finally reveal the origin of the "Cow".